Check with the 409 guys. That same pulley was used on the 63-65 high performance 409. Also check with the Corvette guys. It was also used on the 69-79 Corvette big blocks and small blocks in various configurations. Then there's the 65-67 Chevelle 396. That also came with that pulley (with AC and 62 amp alternator). Not to mention the police cars from the early 70's. Heck, it was even used on the 74/75 Vega!

But to answer your question, it's still available from GM. Go to GMPARTSDIRECT.COM and put in 3844100. $20.39 plus shipping!